LimnologicalEvaluation of Review trophic (2012) level of12, the 2: largest79-85 dimictic lakes of western based on the Carlson criteria 79 DOI 10.2478/v10194-011-0047-8

Evaluation of trophic level of the largest dimictic lakes of based on the Carlson criteria

Jacek Kubiak, Sylwia Machula, Katarzyna Stepanowska, Marcin Biernaczyk

Department of Hydrochemistry and Aquatic Biological Resources, West Pomeranian University of Technology in , Kazimierza Królewicza 4, 71-550 Szczecin, Poland; e-mail: [email protected]

Abstract: Between the years 1970-2010, using the Carlson model criteria, the rate of eutrophication and trophic level of the largest dimictic lakes of Western Pomerania were studied. It was found that during the testing period, Lake Ińsko Duże was a mesotrophic reservoir, and Lakes Wądół, Będzin and Ińsko Małe were characterized by a highly advanced eutrophy. Lakes Woświn, Morzycko, Krzemień, Chłop Duży and Jelenin had borderline characteristics between being mesotrophic and eutrophic, while Lakes Narost, Chłop Mały and Wisala were typically eutrophic reservoirs. During the study, changes in the trophic level of Lakes Ińsko Duże and Morzycko and Woświn were noted. The first of the reservoirs listed had the best water quality in the second half of the 1990s, during which time the other two lakes had the worst water quality, taking into account the whole study period. Such changes were not observed in the other reservoirs examined. Key words: eutrophication, trophic level, Carlson Criteria, Western Pomeranian lakes

Introduction cation has led, and continues to lead, to a decrease in the quality and disturbances in the biocenotic balance In the context of the complex problem of envi- of the waters, and is visible even in the water bodies ronmental pollution, great importance is attributed to under special protection: in national parks. the process of over-fertilization of surface waters, with Anthropopressure makes the abiotic factors, eutrophication being a very important issue in their subject to quick changes, have a decisive impact on protection. Urbanization, industrialization and inten- the functioning of hydrobiocenoses. The process has sive agricultural production in the catchment area, as been reinforced in surface waters due to urbanization well as a significant development of tourism, with a and intensive development of industry and agricul- lack of effective methods of protecting the lakes, af- ture. As a consequence, in the West Pomeranian Lake fect them negatively and increase loading of biogenic District, as in other Polish regions, the surface waters substances, especially phosphorus and nitrogen. This have been going through the process of eutrophica- condition resulted in recent decades in the rapid eu- tion, constituting an extremely important problem in trophication of lakes, and loads of biogenic elements their protection, particularly in relation to lakes (Ku- are often above the levels considered by Vollenweider biak 2003). (1989) to be dangerous. The high rate of eutrophica- The increase in trophic level of lakes causes a tion and high trophic level of surface waters, especial- decrease in their value in use: reducing the environ- ly lakes, have become a global problem. The changes mental values of lakes, their tourist and recreational negatively impacting human life, and at the same time attractiveness, as well as the possibility of their usage brought about by mankind, escalated in the 1930s, and for fishing (Vollenweider 1971; Lossow 1995; Kalff now in many countries, including Poland, have grown 2002; Kubiak 2003). This results in measurable eco- to a dangerous size. The ongoing process of eutrophi- nomic losses. It is also considered that eutrophication 80 Jacek Kubiak, Sylwia Machula, Katarzyna Stepanowska, Marcin Biernaczyk is the greatest threat to the biodiversity of freshwa- Materials and Methods ter habitats (Hillbricht-Ilkowska 1998). The economic importance of the lakes and the need to protect them The study covered the greatest (of a surface area are undisputed. In Poland, too, the escalation of the larger than 100 ha) dimictic lakes in Western Pomera- process of eutrophication has been observed (Kubiak nia located in the following areas: 2003). • Ińskie Lake District in the catchment of the upper Lakes are particularly sensitive to contami- River , ie. Lakes Ińsko Duże, Wisala, Ińsko Małe nants; they often do not return to their original state (Odnoga Linowska) and Krzemień; even after elimination of the source of contamination. • Myśliborskie Lake District, in the western part, Protection and restoration of lakes, especially those Lakes Morzycko, Narost and Jelenin and in the degraded, is extremely difficult and requires removal eastern part, situated in the catchment of the River of the causes of degradation and knowledge of the Myśla, Lakes Wądół (Lipiańskie Północne), Będzin, complex ecosystem of the lake, the right choice of Chłop Wielki and Chłop Mały. methods of restoration, and a consistent, often long- • Also Lake Woświn, in the catchment area of the term study (Lossow 1995; Choiński and Ptak 2009) River , north of the Ińskie Lake District and of their effectiveness. The costs of these works must Lake Miedwie, located in the Plains, have be borne to prevent the degradation of lakes (Lossow been included in the research. 1995). Putting in order the wastewater management, In the present study, the results of the authors’ and changes in soil use in the lake catchment areas own research as well as materials from the Department are just two of the ways to protect lakes, which can of Hydrochemistry and Water Protection of the West improve the quality of their waters. Pomeranian University of Technology in Szczecin Given the economic importance of lakes, the have been used. Some of the earlier results for Lakes need to protect them, and the impact of eutrophica- Morzycko, Będzin and Wądół were collected from the tion on the water quality in these reservoirs, in the materials of the State Inspectorate for Environmental present study the eutrophic levels and their changes in Protection (OBiKŚ 1977). The geographical position the years 1970-2010 in the largest (over 100 ha) strati- of the lakes studied and selected morphometric indi- fied lakes of Western Pomerania have been presented. cators of their basins are given in Table 1.

Table 1. Geographical position and selected morphometric indicators of the lakes studied Ińsko Lake Będzin Chłop Ińsko Małe Jelenin Krzemień Miedwie Morzycko Narost Wądół Wisala Woświn Duże Location: Latitude [°]: 52.984 53.000 53.444 53.432 52.910 53.376 53.268 52.862 52.882 53.008 53.415 53.525 Longitude [°]: 14.941 14.900 15.554 15.514 14.446 15.554 14.883 14.410 14.505 14.955 15.555 15.412 Elevation above sea level [m]: 59.7 60.1 127.0 127.0 71.0 91.7 13.0 51.4 59.0 61.4 112.2 78.9 Shape: Maximum length [m]: 3135 3800 5400 2950 2500 3510 16200 2900 2525 3015 3415 9500 Maximum width [m]: 710 1125 2100 725 1400 1030 3160 2400 625 755 940 2000 Average width [m]: 445 860 901 345 417 653 2177 1182 427 512 531 852 The length of coastline [m]: 8250 16850 31450 7600 7375 8300 38800 12025 6600 11850 12112 26075 Surface: total catchment area [km2] 206.1 28.8 40.6 9.8 14.3 85.0 10117 66.0 23.6 7.1 53.4 56.3 immediate catchment area [km2] 5.4 8.8 15.9 6.8 14.3 11.4 570 9.81 8.5 7.1 7.81 31.8 water surface [ha] 139.6 326.7 486.6 101.8 104.3 229.1 35270 342.7 107.9 154.5 181.5 809.1 Depth: maximum [m] 15.4 32.9 41.7 11.7 21.4 29.2 43.8 60 13.2 15.9 15.4 28.1 Average [volume/surf. of w. table] 4.5 10.7 12.9 5.9 8.8 9.6 19.3 14.5 6.3 5.3 5.9 9.4 Volume: Total volume [dam3] 6247.4 34887.3 62613.3 6009.7 9142.4 21924.0 681672.4 49826.9 6827.0 8249.8 10682.2 75840.8 Evaluation of trophic level of the largest dimictic lakes of western Pomerania based on the Carlson criteria 81

The analysis of the trophic level of lakes was trations recorded were below 0.048 mg P dm–3; they based on the Carlson method (1977), and on the rate were higher only in the years 1982 and 1987 (0.068 of oxygen consumption (RAOD – relative areal oxygen mg P dm–3). Lower concentrations of total phospho- deficit) in the hypolimnion during formation of the rus in comparison with other reservoir studies were summer stratification, calculated using the method found also in Lake Miedwie; usual values during listed by Wetzel (2001) and Kalff (2022) introduced summer stagnation in the surface waters were in the by Strøm (1931) and modified by Hutchinson (1938, range of 0.055-0.060 mg P dm–3. This range of con- 1957). Hydrochemical studies, i.e. regarding the total centrations resulted in the TSI calculated according phosphorus and chlorophyll a concentration, were to the Carlson model (1977) for these reservoirs at- conducted in accordance with the generally accepted taining typically the levels from 55 to 60, indicating methodology (APHA 1981, 1995). that the waters of these lakes were in advanced stages The results obtained were analysed with the sta- of mesotrophy. Higher concentrations of phosphorus tistics program Statistica 9.0 (StatSoft, Inc. 2010) and than those reported for Lakes Ińsko Duże and Mied- are presented in the paper’s tables. wie have been measured in Lake Chłop Duży (range 0.050-0.070) and on occasion, especially in the 1980s, Results in Lakes Krzemień and Morzycko. These phosphorus concentrations indicated a moderately low eutrophy Under the Carlson system (1977), in assessing level (TSI range of 60-65). The highest values of this the trophic status of lake water the following elements particular indicator (above 0.100 mg P dm–3) were re- are taken into consideration: measurements during corded for Lakes Wądół, Będzin and Ińsko Małe, as the summertime of concentrations of total phospho- well as Narost and Wisala reservoirs. The phosphorus rus and chlorophyll a in the surface waters, and Secchi concentration for these lakes, and the trophic status depth. The present chapter will discuss the values of indicators calculated on their basis, clearly point to a these indicators found in the studied lakes in the years considerable degree of advancement of the process of 1970-2010, and the trophic status indicators (TSI) cal- eutrophication (strong eutrophy). culated in accordance with the system applied. The concentration of chlorophyll a in the stud- Total phosphorus concentrations in surface ied reservoirs varied within the range between 11.0 to waters of the lakes under consideration during the 55.0 mg m–3, with an average concentration of 22.5 mg period of the study were on average 0.089, with the m–3 for the years 1970-2010; most often (43.7% of the range of variation from 0.030 to 0.222 mg P dm–3. The cases) the concentration stood between 20.0-25.0 mg lowest concentrations were below 0.051, and the high- m–3 (Table 2). est above 0.130 mg P dm–3 (respectively, 10% of meas- The lowest concentrations of chlorophylla were urements in each of the ranges). The total phosphorus recorded for the waters of Lake Ińsko Duże through- concentrations for the summertime in the surface wa- out the entire study period, and Lake Krzemień in the ters of the lakes surveyed are shown in Table 2. late 1970s and early 1980s; these concentrations stood The lowest values of this indicator were meas- at 15 mg m–3 and below. Similar values of this indica- ured in Lake Ińsko Duże: in most cases the concen- tor were found for the most part also in the surface

Table 2. Selected statistical indicators of the concentrations of total phosphorus and chlorophyll-a in the surface waters of the studied lakes and Secchi depth during the summer stagnation

Indicator N Average Minimum Maximum Max. frequency range Total phosphorus 140 0.089 0.030 0.222 0.080-0.100 (26.6%) Chlorophyll a 140 22.5 11.0 55.0 20.0-25.0 (43.7%) Secchi depth 140 1.97 0.40 4.30 1.0-2.0 (39.2%) TSI-TP 140 66.1 53.2 82.1 65.0-70.0 (48.9%) TSI-Chl 140 60.4 54.1 69.9 58.0-62.0 (56.3%) TSI-SD 140 51.6 39.0 73.2 45.0-55.0 (58.3%) TSI – trophic status indicators (scale 0-100); Measurement units: total phosphorus – mg P dm–3, chlorophyll a – mg m–3, Secchi depth – m 82 Jacek Kubiak, Sylwia Machula, Katarzyna Stepanowska, Marcin Biernaczyk waters of Lake Miedwie. In later years, the value of hand remained a mesotrophic reservoir, with its best this indicator has significantly increased (20 mg m–3) water quality in the late 1990s, while in Lakes Morzy- in these two reservoirs. Slightly higher (16-20 mg m–3) cko and Woświn reduced water quality was observed concentrations of chlorophyll a were recorded for the during the 1990s. The other reservoirs in the entire waters of Lake Woświn. For the first three reservoirs study period were characterized by a similar stage listed above, the TSI value was typically 56-58, while of eutrophication. Based on the research conducted, for Lake Woświn it was 60, indicating, respectively, a these reservoirs can be divided into three groups: highly advanced mesotrophy and the transition state • the first group, including Lakes Będzin, Wądół and between mesotrophy and eutrophy. Decidedly the Ińsko Małe, where an advanced process of eutroph- highest (>30 mg m–3) chlorophyll a concentrations ication was recorded, the rate of oxygen consump- were measured in Lakes Będzin, Wądół, Ińsko Małe tion RAOD during the formation of the summer and Narost; slightly lower values (>25 mg m–3) were heterothermy was the highest (>100 µg dm–3 d–1) recorded in Lake Wisala. Such values of this indicator for these reservoirs (Table 3), suggest an intensive ongoing process of eutrophica- • the second group, with Lakes Narost, Chłop Mały tion in these reservoirs, and a high level of eutrophy. and Wisala, with characteristics typical for eutro- The other lakes, taking into account the indicator be- phy, and oxygen consumption rate RAOD from 75 ing discussed, were characterized by average eutrophy to 96 µg dm–3 d–1 (Table 3), levels (the concentration of chlorophyll a in the range • the third group, made up of Lakes Woświn, Morzy- of 20-25 mg m–3, and TSI 59-63). cko, Miedwie, Krzemień, Chłop Duży and Jelenin, Another determining indicator for the trophic with systems typical for the borderline between level in the Carlson model (1977) is the Secchi disk vis- mesotrophic and eutrophic (oxygen consumption ibility (Secchi depth). In the studied lakes, it varied dur- rate of 49-64 µg dm–3 d–1; Table 3). Outside of these ing the study period from 0.4 to 4.3 m, usually ranging groups remains Lake Ińsko, where the rate of oxy- between 1.0-2.0 m (Table 2). During the summer, the gen consumption (Relative Areal Oxygen Deficit) water transparency was the highest in Lake Ińsko Duże: was less than 40 µg dm–3 d–1 (Table 3). for the whole period it was always above 2.8 m, and at the end of the 1990s it ranged from 4.0 to 4.3 m. These Discussion values were indicative of low value mesotrophy (TSI of 39-43). Water transparency of less than 1.0 m was re- Lakes are dynamic ecosystems that change corded for Lakes Wądół, Będzin (TSI over 65) and less over time in order to enrich and intensify the biologi- often also in Lake Narost; it clearly indicated the strong cal production. Transport, exchange and redistribu- eutrophy of the waters of these reservoirs. In the other tion of mineral matter, derived from biogeochemical lakes, the indicator discussed was at the level charac- processes, organic matter produced in the ecosystem teristic for the waters on the borderline between mes- and contaminants introduced into the environment otrophic and eutrophic, or for weak eutrophy. are the processes determining the direction and rate In the studied lakes of Western Pomerania, the of lake evolution (Gotkiewicz et al. 1990; Lossow changes in the respective indicators characterizing and Więcławski 1991). In the local conditions, these each stage of the process of eutrophication were re- processes are dependent on the whole set of factors: corded during the study period. Lake Będzin, and in climatic, hydrological, hydrogeological and soil con- particular Lake Wądół were throughout the whole pe- ditions in the catchment area. In addition, they are riod strongly eutrophic. Lake Ińsko Duże on the other impacted by the morphometric characteristics and

Table 3. The rate of oxygen consumption (RAOD) in the hypolimnion waters in the studied lakes during the formation of the summer stagnation

Chłop Chłop Ińsko Ińsko RAOD \* Będzin Jelenin Krzemień Miedwie Morzycko Narost Wądół Wisala Woświn Duży Mały Duże Małe

µg dm–3 d–1 137.2 49.0 75.0 31.7 106.9 63.0 50.1 43.5 63.7 83.4 149.0 96.6 63.7 mg cm–2 d–1 0.053 0.044 0.048 0.040 0.051 0.045 0.046 0.043 0.046 0.049 0.057 0.046 0.045 \* - Relative areal oxygen deficit (Strøm 1931, Hutchinson 1938, 1957) Evaluation of trophic level of the largest dimictic lakes of western Pomerania based on the Carlson criteria 83 hydrochemical relations of the reservoir (Olszewski In the case of Lake Wądół, the catchment area and Tadajewski 1959; Lossow 1996; Stumm and Mor- is a highly urbanized area, and the reservoir was used gan 1996; Kalff 2002). Of key importance to the lake for recreational purposes, and for a number of years it are also the dynamics of water masses (Patalas 1960), was also a collector of municipal wastewater. In both the functioning of its biocenosis, and exchange of ele- of these lakes, the unfavourable ratio of the volume of ments between the solid phase and solution (Olsze- the lake basin to the length of the developed shoreline wski and Tadajewski 1959; Stumm and Morgan 1996; caused the pollution load flowing from the catchment Kalff 2002). These factors determine the intensity of area to be received by a small volume of water. Such lakes’ eutrophication process (Table 4). natural conditions resulted in poor water quality, and In the waters of Lakes Wądół and Będzin, the the eutrophication of lakes occurred at a rapid pace characteristics indicating a very high trophic level (Kubiak 2003). were observed through the whole study period, which Lakes Chłop Mały, Ińsko Małe, Wisala and was primarily due to their high susceptibility to deg- Narost according to the Carlson criteria (1977) were radation (Kubiak 2003). This was reinforced by the eutrophic throughout the whole study duration. They tachymictic type of water mass mixing, their shallow- were characterized by a tachymictic (Chłop Mały, ness, developed coastline and the small volume of the Ińsko Małe, Wisala) or eumictic, with inclination to lake basin (Kubiak and Tórz 2005, 2006). Lake Będzin’s tachymictic (Narost) water mass mixing (Kubiak and catchment area was intensively cultivated. Other pa- Tórz 2005, 2006). rameters which characterize the area’s susceptibility In these lakes, a major part of the lake bottom to degradation were also adverse: it is a flow-through in the summer remained in the range of warm epilim- lake, and a reservoir of this type is subject to high nion, resulting in rapid recirculation of nutrients from loading of matter from the outside, and is therefore bottom sediments into the water. The natural charac- particularly at risk of eutrophication (Hillbricht-Il- teristics of the catchment area favoured surface runoff, kowska and Kostrzewska-Szlakowska 1996). (eg. lack of area), and therefore the pressure on the

Table 4. Mean values of trophic levels after Carlson (1977) in the waters of the lakes surveyed in the studied period

Indicator Będzin Chłop D Chłop M Ińsko M Ińsko D Jelenin Krzemień Miedwie Morzycko Narost Wądół Wisala Woświn %O – summer; 2 0.4 19.3 6.5 6.7 36.6 6 .8 7.2 14.1 7.0 4.5 0.0 0.1 6.0 bottom TN – summer; 2.372 1.612 1.751 2.436 1.834 1.819 1.395 0.736 1.753 1.777 3.591 1.728 2.156 surface TP – summer; 0.111 0.061 0.093 0.103 0.048 0.083 0.080 0.048 0.083 0.097 0.407 0.095 0.077 surface TP – average 0.121 0.067 0.082 0.081 0.039 0.056 0.100 0.075 0.071 0.066 0.258 0.072 0.091 TN/TP 20.2 26.7 19.6 25.5 40.1 22.4 18.2 37.3 22.5 18.3 9.7 18.1 28.3 Chl a – summer 33.0 19.6 25.2 31.7 17.6 19.2 16.0 11.0 20.3 27.3 46.6 23.4 19.1 Chl a – spring 15.5 10.6 13.8 12.4 11.3 11.8 7.6 5.0 8.8 11.4 26.6 9.8 11.7 Chl a – average 24.2 14.5 19.6 21.8 14.5 15.6 12.0 10.0 14.6 19.4 34.1 17.0 15.4 SD – summer 0.6 2.3 1.8 1.4 3.7 2.6 2.2 2.8 2.4 1.3 0.6 1.6 2.2 SD – spring 1.7 2.8 2.4 2.3 4.7 4.2 3.2 3.4 3.2 2.0 1.1 2.3 3.3 SD – average 1.1 2.6 2.1 1.8 4.2 3.4 2.7 3.0 2.7 1.6 0.9 2.2 2.8 68 48 52 55 41 46 49 45 48 57 66 53 48 TSI-SD (summer) EU ME ME ME ME ME ME ME ME ME EU ME ME 65 60 62 64 59 60 58 54 60 63 68 62 59 TSI-Chl (summer) EU ME EU EU ME ME ME ME EU EU EU EU ME 72 63 70 71 60 68 67 60 68 70 91 70 67 TSI-TP (summer) EU EU EU EU ME EU EU ME EU EU EU EU EU

SD – Secchi depth, Chl a – chlorophyll concentration, TP – total phosphorus concentration, TN – total nitrogen concentration, % O2 – oxy- genation level, ME – mesoeutrophy, EU – eutrophy 84 Jacek Kubiak, Sylwia Machula, Katarzyna Stepanowska, Marcin Biernaczyk lakes was large, resulting in their rapid eutrophication catchment area conditions. The catchment area with (Bajkiewicz-Grabowska 1990; Kudelska et al. 1994). In a prevalence of farmland and forest and some build- addition, intense eutrophication of these reservoirs ings took part in its entirety in the delivery of biogen- was further reinforced by the usage of the catchment ic loads to the lake; it showed, however, only average area, with a substantial share of farmland. Further- loading of the matter deposited in the catchment area more, the eutrophication has been intensified as a (Bajkiewicz-Grabowska 1990). The rate of eutrophica- result of unfavourable morphological conditions of tion of the lake was moderate (Kubiak 2003). the lake basin (small basin volume with considerable The assessment of the trophic level of Lake length of coastline, thus the load of pollutants flow- Miedwie according to the Carlson criteria (1977) has ing from the catchment area was collected by a small shown that it is currently a mesotrophic reservoir volume of water). with elevated concentrations of phosphorus (typical Lakes with borderline meso-and eutrophic for eutrophy). Earlier, in the 1990s, it was a eutrophic characteristics throughout the study were Lakes Chłop water body. The studies conducted showed that the Duży, Morzycko, Jelenin, Krzemień and Woświn; only reservoirs less resistant to anthropopressure, with in Lake Morzycko did the eutrophic characteristics catchment areas favourable to surface runoff, had the prevail over the mesotrophic. All these reservoirs were trophic level high enough that it was impossible to de- medium-resistant to degradation, except for the high- termine significant trophic level fluctuations in them. ly resistant Lake Morzycko (Kubiak 2003; Kubiak and On the other hand, the highly degradation resistant Tórz 2004). The catchment area conditions in which lakes did not show such trends, as they were effectively the catchment area was little or moderately suscep- protected from the impact from the outside thanks to tible to loading of biogenic matter stored in its area their natural features. It was also found that the reser- caused the variations in the rate of eutrophication: voirs studied had varied trophic levels; the lakes with slow for Lakes Jelenin and Chłop; moderate in Lakes lower trophic status (Ińsko Duże, Chłop Duży, Jelenin) Morzycko, Krzemień and Woświn (Kubiak 2003). The had, during the summertime, lower water dynamics slower pace of eutrophication was due to the agricul- and a more marked stratification of water masses. This tural and forest character of the immediate catchment has caused a limited penetration of biogenic elements area, reducing its capacity for loading of biogenic mat- from the hypolimnion to the euphotic layer (Patalas ter accumulated in the area. The favourable conditions 1960; Kalff 2002). of the catchment area resulted in meso-eutrophy of Lakes Chłop Duży and Jelenin. On the other hand, in References the case of Lakes Krzemień and Woświn this state of affairs (despite the adverse conditions in the catch- [APHA] American Public Health Association, 1981, Stan- ment area) was the result of the lake basin features dard Methods for the examination of water and waste- such as greater lake depth and volume. The tendency water, Amm. Publ. Health Ass. Inc., New York, p. 1966. [APHA] American Public Health Association, 1995, Stan- of Lake Chłop Duży to bradymictic mixing of wa- dard methods for the examination of water and waste ter masses, with high resistance to degradation and water, Amm. Publ. Health Ass., New York, p. 1956. low catchment area susceptibility to biogene load- Bajkiewicz-Grabowska E., 1990, Stopień naturalnej ing, meant that the advancement of the eutrophica- podatności jezior na eutrofizację na przykładzie tion process in the reservoir was the lowest among the wybranych jezior Polski (Degree of natural susceptibil- meso-eutrophic lakes. ity to eutrophication of lakes, based on selected Polish The mesotrophic Lake Ińsko Duże had medium lakes), Gospod. Wod. 12: 270-272 (in Polish). or high resistance to degradation; this was favoured by Carlson R.F., 1977, A trophic state index for lakes, Limnol. Oceanogr. 22(2): 361-369. the lake’s significant depth, eumictic – with inclination Choiński A., Ptak M., 2009, Lake Infill as the Main Factor to bradymictic – water mass mixing type and a signifi- Leading to Lake’s Disappearance, Polish J. of Environ. cant share of hypolimnion in the total volume of the Stud. 18 (3): 347-352. lake (Kubiak 2003). The small surface of the lake bot- Gotkiewicz J., Hutorowicz H., Lossow K., Mosiej J., Pawłat tom within the epilimnion has reduced the intensity H., Szymczak T., Traczyk T., 1990, Czynniki kształtujące of the recirculation of biogenic elements from the sed- obieg wody i biogenów w krajobrazie młodoglacialnym iment layer to the trophogenic layer. High resistance (Factors affecting the circulation of water and nutrients to degradation balanced out the unfavourable lake in the postglacial landscape), [in:] Ryszkowski L. Mar- cinek K., Kędziora A. (eds), Obieg wody i bariery bio- Evaluation of trophic level of the largest dimictic lakes of western Pomerania based on the Carlson criteria 85

geochemiczne w krajobrazie rolniczym (The water cycle Lossow K., 1995, Odnowa jezior (Restoration of lakes), Eko- and biogeochemical barriers in agricultural landscape), profit. 5: 11-15 (in Polish). Wyd. Nauk. UAM, Poznań: 105-126 (in Polish). Lossow K., 1996, Znaczenie jezior w krajobrazie Hillbricht-Ilkowska A., 1998, Różnorodność biologiczna młodoglacialnym pojezierza Mazurskiego (The impor- siedlisk słodkowodnych – problemy, potrzeby, działania tance of the lakes in the landscape of the Masurian Lake (Biological diversity of freshwater habitats – problems, District), Zesz. Probl. Post. Nauk Rol. 431: 47-59 (in Pol- needs, activities), Idee Ekol. Ser. Szkice 13(7): 13-55 (in ish). Polish). Lossow K., Więcławski F., 1991, Migracja podstawowych Hillbricht-Ilkowska A., Kostrzewska-Szlakowska I., 1996, pierwiastków pożywkowych z gleb, użytkowanych rol- Ocena ładunku fosforu i stanu zagrożenia jezior rze- niczo do wód powierzchniowych (Migration of the ba- ki Krutyni (Pojezierze Mazurskie) oraz zależności sic elements of nutrients from soils used for agriculture pomiędzy ładunkiem a stężeniem fosforu w jeziorach to surface waters), Biul. Inf. ART Olszt. 31: 123-133 (in (Phosphorus load rating and level of risk of lakes of the Polish). River Krutynia (Masurian Lakeland) and the relation- [OBiKŚ] Ośrodek Badań i Kontroli Środowiska, 1977, Atlas ship between the load and the concentration of phos- czystości jezior województwa szczecińskiego 1970-1976 phorus in lakes), Zesz. Nauk. Kom. Nauk „Człowiek i (Atlas of lake quality conditions in voivodship of Szc- Środowisko” PAN 13: 97-123 (in Polish, English sum- zecin 1970-1976) [typescript], Szczecin (in Polish). mary). Olszewski P., Tadajewski A., 1959, Wpływ zlewni na żyzność Hutchinson G.E., 1938, Chemical stratification and lake jezior (Effects on fertility of basin lakes), Zesz. Nauk. morphology, Proc. Nat. Acad. Sci. USA 24: 63-69. WSR Olszt. 4: 191-194 (in Polish, English summary). Hutchinson G.E., 1957, A Treatise on Limnology. Vol I. Ge- Patalas K., 1960, Mieszanie wiatrowe jako czynnik określa- ography, Physics and Chemistry, Wiley, New York, p. jący intensywność krążenia materii w różnych morfo- 1015. logicznie jeziorach okolic Węgorzewa (Mixing of wind Kalff J., 2002, Limnology, Prentice Hall Ltd., New Jersey, p. as a factor determining the intensity of circulation of 592. matter in morphologically different lakes surrounding Kubiak J., 2003, Największe dimiktyczne jeziora Pomorza Za- Węgorzewo), Rocz. Nauk Rol. Ser. B 77(1): 224-241 (in chodniego. Stan trofii podatność na degradacje oraz wa- Polish, English summary). runki siedliskowe ichtiofauny ( The Largest dimictic La- StatSoft , 2010, STATISTICA (data analysis software sys- kes of Western Pomerania: Trophic status, susceptibili- tem), version 9.0. ty to degradation, and habitat conditions for fish fau- Strøm K.M., 1931, Feforvatn: A physiographic and biologi- na), Rozprawy ARSzcz. 214, Szczecin, p. 96 (in Polish, cal study of a mountain lake, Arch. Hydrobiol. 22: 491- English summary). 536. Kubiak J., Tórz A., 2004 , Variations In the trophic state of Stumm W., Morgan J., 1996, Aquatic chemistry. Chemi- the mesotrophic Ińsko Duże Lake (1970-2002), Limnol. cal equilibrium and rates in natural waters, Wiley, New Rev. 4: 115-124. York, p. 1022. Kubiak J., Tórz A., 2005, Water mass dynamics in the largest Vollenweider R.A., 1971, Scientific fundamentals of the eu- stratified lakes of western Pomerania in relation to their trophication of lakes and following waters, with particu- trophic status, Limnol. Rev. 5: 129-136. lar reference to nitrogen and phosphorous as factors in Kubiak J., Tórz A., 2006, Thermal regime of the biggest di- eutrophication, OECD, Paris, p. 61. mictic lakes of Western Pomerania region, Limnol. Rev. Vollenweider R.A., 1989, Global problems of eutrophication 6: 155-162. and its control, Symp. Biol. Hung. 38: 19-41. Kudelska D., Cydzik D., Soszka H., 1994, Wytyczne monito- Wetzel R. G., 2001, Limnology, W.B. Saunders Company, ringu podstawowego jezior (Guidelines for basic moni- Philadelphia, p. 743. toring of lakes), PIOŚ, Warszawa, p. 42 (in Polish).